The present invention relates to a control system for barrier fluid circulation used in double seal-type shaft seals typically used in pumps and other rotating equipment. Typically, barrier fluids use an external supply of cooling fluid such as water which aids in sealing and can serve to cool the seals.
Double seals are used in severe sealing conditions. A barrier fluid is introduced between the seals to serve several purposes, including: to lubricate and cool the outboard seal that normally does not see the working fluid; or to flush or dilute any working fluid (actual fluid being pumped by the pump) that should leak past the inboard seal; or to lubricate the inboard seal when the working fluid has poor lubricating qualities; or to cool the inboard seal. Double seal installations typically utilize barrier fluids in one of two ways: a closed system using pressure tanks and heat radiators and a recirculating system for continuously reusing the barrier fluid; or an open flush system where a continuous supply of barrier fluid passes through the seal arrangement only once before disposal or collection.
For an open flush system, modern environmental laws and conservation efforts demand improved monitoring and control to minimize the barrier fluids used in these systems. It is advantageous for a system to allow the user to establish the minimal flow rate that is necessary to cool the seal while maintaining the necessary barrier fluid pressure.